Re: [eclipselink-users] (bug?) counting results gives a cartesian produc

[Yannick Majoros <yannick.majoros@xxxxxxxxx>]

Hello,

I solved it like this, but it's somewhat hacky. It works, but is there a 
better way?

        Set<Root<?>> rootSet = selectQuery.getRoots();
        if (rootSet.isEmpty()) {
            throw new RuntimeException("Expecting a query root");
        }
        if (rootSet.size() > 1) {
            throw new RuntimeException("Cartesian product");
        }
        List<Root<T>> roots = new ArrayList(rootSet);
        Root<T> firstRoot = roots.get(0);
        Expression<Long> countExpression = builder.count(firstRoot);

Best regards,

Yannick Majoros

Le 2/05/2012 15:56, James Sutherland a écrit :
> You cannot use the restriction from one query in another.  You restriction
> will be based on a different entityRoot , so you end up with two entityRoots
> as expected.
>
> You have the build the where using the correct entityRoot from the query
> that you are building.
>
>
> ymajoros-2 wrote:
> > Hello,
> >
> > After upgrading to 2.3.3, I get a cartesian product. It could have been
> > the same in 2.3.2, but I didn't notice it then.
> >
> > Here is a method which counts the total results of query (for pagination):
> >
> >       public<T>  Long countCriteriaQueryResults(CriteriaQuery<T>
> > selectQuery) {
> >           CriteriaBuilder builder = entityManager.getCriteriaBuilder();
> >
> >           CriteriaQuery<Long>  countQuery = builder.createQuery(Long.class);
> >           Class<T>  resultType = selectQuery.getResultType();
> >           Root<T>  entityRoot = countQuery.from(resultType);
> >           Expression<Long>  countExpression =
> > builder.countDistinct(entityRoot);
> >           countQuery.select(countExpression);
> >           countQuery.where(selectQuery.getRestriction());
> >
> >           return entityManager.createQuery(countQuery).getSingleResult();
> >       }
> >
> > It results in this, for example:
> >
> > SELECT COUNT(DISTINCT(t0.ID)) FROM client t0, client t1 WHERE
> > ((t1.FIDUCIAIRE_ID = ?) = ?)
> >
> > I'd rather want this:
> >
> > SELECT COUNT(DISTINCT(t1.ID)) FROM client t1 WHERE ((t1.FIDUCIAIRE_ID =
> > ?) = ?)
> >
> > Is it a bug in Eclipselink or is my code wrong?
> >
> > Is it ok to use the previous predicates with query.getRestriction()?
> >
> > Best regards,
> >
> > Yannick Majoros
> > _______________________________________________
> > eclipselink-users mailing list
> > eclipselink-users@xxxxxxxxxxx
> > https://dev.eclipse.org/mailman/listinfo/eclipselink-users
>
> -----
> http://wiki.eclipse.org/User:James.sutherland.oracle.com James Sutherland
> http://www.eclipse.org/eclipselink/
>   EclipseLink ,  http://www.oracle.com/technology/products/ias/toplink/
> TopLink
> Wiki:  http://wiki.eclipse.org/EclipseLink EclipseLink ,
> http://wiki.oracle.com/page/TopLink TopLink
> Forums:  http://forums.oracle.com/forums/forum.jspa?forumID=48 TopLink ,
> http://www.eclipse.org/forums/index.php?t=thread&frm_id=111&S=1b00bfd151289b297688823a00683aca
> EclipseLink
> Book:  http://en.wikibooks.org/wiki/Java_Persistence Java Persistence
> Blog:  http://java-persistence-performance.blogspot.com/ Java Persistence
> Performance